1. Field of the Invention
The present invention relates to wiring techniques and systems, particularly where a wire forming an electrical path for carrying electric power, or a group of such wires, pass from a substantially stationary member through a rotatable member and continue to another substantially stationary member. The invention has particular utility where an electric wire or group of electric wires pass through a rotatable member which has limited rotational travel, such as the steering wheel of a motor vehicle, for example.
2. Prior Art
The passage of a wire or group of wires, sometimes referred to as a harness, carrying electric current through a rotatable member without interrupting the continuity of the electrical path, has been addressed and a solution to the problem generated by such structure has been presented, one solution to the problem lies in the use of a combination of conductive pins mounted in an insulated mounting and a plate with a conductive track on the plate. The conductive pins and the plate are mounted in such a manner so as to accord electrical contact between the conductive pins and the conductive track while the pins and the track move relative to each other.
The conventional steering wheel of a motor vehicle offers a good example of apparatus which has the type of problem involved. As represented in the drawings, and labeled Prior Art, it has been long standing practice to locate the horn button or horn switch for a motor vehicle on the upper or top side of the steering wheel of the vehicle, for the convenience of the driver of the vehicle. The steering wheel is mounted at one end a steering shaft which, at its other end, connects to the steering mechanism of the vehicle. The steering wheel is conventionally mounted on the steering shaft above a steering column, which surrounds the steering shaft. The steering wheel and steering shaft are rotatable while the steering column is stationary. The steering wheel and steering shaft are rotated in unison both clockwise and counterclockwise, for steering the vehicle to the left and right while the surrounding steering column remains stationary. The rotational travel of a steering wheel and shaft is normally no more than two full turns in both directions, from straight ahead steering.
In the past, a horn button or switch was located on the steering wheel with a single conductor such as a wire, extending from the horn button. The wire extended from the rotatable steering wheel to the stationary steering column. With a single conductor or wire, the wire could be loosely draped or wrapped or coiled around the steering shaft so that the wire would tighten and loosen about the shaft as the steering wheel and shaft were rotated. With a single wire connecting the rotatably moving horn button with a stationary terminal on the steering column and the limited rotational travel of the steering wheel, steering shaft and the horn button, a complex interconnect was not required.
As more features were added to motor vehicles, such as cruise control and audio systems, for example, additional buttons or switches were added to the motor vehicle to control the additional features.
It became desirable to locate some of these additional control buttons or switches in the hub of the steering wheel for driver or operator convenience.
With the additional buttons or switches located in the hub of the steering wheel it became desirable to arrest the hub of the steering wheel so as to place the hub of the steering wheel in a non-rotation state, irrespective of the rotation of the steering wheel. U.S. Pat. No. 4,808,146 teaches apparatus for generating the non-rotation state of the hub of a steering wheel irrespective of the rotational travel of the steering wheel in which the arrested hub is located.
The increase in the number of buttons or switches located in the hub of the steering wheel increased the number of wires threaded around the steering shaft and it was no longer practical to loosely wind the wires around the steering shaft, from the standpoint of wear on the wires and economy. The wire harness, now being much larger in diameter and heavier in weight, would wear faster and the many loose turns of wire around the steering shaft would be a cost factor.
This problem was overcome by the use of a combination or an interconnect of a plate with a plurality of conductive, isolated tracks and a set of condutive, isolated pins riding on the conductive tracks.
However, with the introduction of apparatus for arresting the hub in the steering wheel for holding the hub in a non-rotation state while the steering wheel is rotated, another set of conductive, isolated pins was added to the electrical interconnect apparatus and another set of conductive, isolated tracks was added to the plate. This decreased the reliability of the electrical interconnect apparatus and further increased the cost of the interconnect apparatus.